What are Altitude and Determination Control Systems (ADCS)?

Attitude Determination and Control System (ADCS) is a crucial subsystem of any spacecraft that controls the altitude and orientation of the spacecraft and provides pointing accuracy and stability for the payload of the spacecraft. It operates based on the information it receives from the ground as well as its onboard sensors. Every spacecraft has 6 degrees of freedom (DOF) which indicates the movement of a spacecraft in a three-dimensional space. Three of them are displacement, and the rest of them are rotation. The attitude determination and control system (ADCS) is responsible for the 3 DOF rotational control of the spacecraft.

ADCS consists of four different segments:

• Sensor System: The sensor module is mainly used for attitude determination. Some of the common attitude sensors that the satellite use is (coarse/fine) sun sensor, earth sensor, IMU, star tracker, and geomagnetic sensor.
• Actuator System: The actuator system is used for attitude control and is used to position the spacecraft in the target attitude by rotating it in 3-axes (yaw, roll, and pitch). Some of the most common ones are the reaction wheel, control moment gyroscope (CMG), thruster, and magnetorquer. 
• Controller: The ADCS Controller will calculate the attitude of the spacecraft using the data coming from the sensors. The Algorithm inside the controller will calculate the targeted attitude and will also determine the rotations needed to accomplish for each axis.
• Interface: The ADCS Interface is the hardware part of ADCS that transmits the signal received from Sensors to the micro-controller and it also distributes the power supply coming from the EPS subsystem to the Actuators.